It was far worse then, as copper places serious upper limits on long-distance high-speed transport. Data transmission latency of copper tends to be 2X that of light (physical bounds, not empirically observed), and making very long cables with copper is impractical due to signal losses. Once long fiber was cheaply available people started to use that for the long links (imagine a toroidal mesh with wrap-around links- the wrap-around links are very long (100+m) and need to be fiber).

However, long fiber causes latency problems- those wrap around links will slow do any global reductions you need to do.

I can't help but imagine wormholes or FTL tech being first invented and used for longer distance interconnects in supercomputers. :-)